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Re: Derivatives

  • To: mathgroup at smc.vnet.net
  • Subject: [mg113727] Re: Derivatives
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Tue, 9 Nov 2010 03:53:28 -0500 (EST)

I think you're asking whether Mathematica can do implicit 
differentiation.  The answer is yes.  Here's a rather simple example.

   eq n= y x^4+4x^2 y+x^ 3== 8 ;
   neweqn = eqn /. y - >y[x] ;
   deriveqn = D[neweqn, x]
   derivative = y'[x]/.First@Solve[deriveqn, y'[x]]
   yvalue = y /. First@Solve[eqn, y]
   derivative /. y[x] - >yvalue


On 11/8/2010 3:37 AM, will wrote:
> Hello,
>
> I am trying to take the derivative (d/dx) of a very messy equation
> that is more easily expressed initially as a function of y, then y and
> a function of x. Rather than have to substitute and expand, can a set
> of equations be input  and instructed to find a derivative wrt x?
>
> (A little bit new to Mathematica)
>
> Thanks.
> Will
>

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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